Handheld chain saws include a saw chain which revolves around the periphery of a guide bar. To drive the saw chain, a sprocket wheel having an externally toothed gear, which is driven by a drive motor, is provided. The external teeth of the sprocket wheel engage between the members of the saw chain and drive them.
The drive shaft of the sprocket wheel is mounted in a housing of the chain saw. A sprocket wheel cover which covers the area of the sprocket wheel is threadably engaged with the housing. At least one stud, which in its mounted state is guided through an opening of the sprocket wheel cover, is fixed to the housing for the threaded fastening. A nut is screwed onto a free thread end of the stud and presses the sprocket wheel cover against the housing.
The guide bar of the saw chain is strung onto the stud, of which there is at least one, and is held clamped between the housing and the sprocket wheel cover. The sprocket wheel cover also has a holding function for the guide bar aside from its protective function.
The sprocket wheel cover is removed for maintenance work on the guide bar or the saw chain or for changing the same components, and also for the space-saving storing of the chain saw; the guide bar including the saw chain can be removed or exchanged. For assembly, first the guide bar is strung onto the at least one stud and then the sprocket wheel cover is attached in such a manner that the at least one stud projects through the opening in the sprocket wheel cover. For completion of assembly, the nut is threaded onto the free thread portion of the stud and tightened. The free thread end of the stud has a maximum usable screw-in depth for the nut. The tightened nut is threadably engaged with an operating screw-in depth that is smaller than the maximum screw-in depth, so that a sufficient tolerance in the tightening direction of the nut remains for the effective tightening without damaging the arrangement.
If the guide bar is removed for extended periods of time, for example for transport or maintenance work, the sprocket wheel cover is re-applied and screwed on even without the guide bar. Thus, it is ensured that the sprocket wheel cover remains on the chain saw. Thus, the sprocket wheel cover will be handy during any later assembly and cannot get lost. In practice, however, it turns out that the at least one nut for fixing the sprocket wheel cover is often pulled too tight when the guide bar is removed. As a result, the sprocket wheel cover and the nut may tilt and become damaged. Depending on the configuration of the arrangement, the actual screw-in depth can exceed the permissible maximum screw-in depth, so that the result can be damage done to the threads on the studs and on the nuts. It is even possible that the studs are ripped out of their anchoring in the housing.